Bone or fracture voids may occur in many different types of bones in many different ways. For example, an unstable distal radius fracture is common especially in the endemic osteoporotic populations of North America, Europe, Asia, and Australia. This type of low energy fracture may be sustained by a fall on an outstretched hand. The classic, osteopenic osteoporotic fragility fracture is extra-articular or includes a simple intra-articular component, i.e., the fracture is primarily outside of a joint or may include a simple component within the joint. The fracture may result in dorsal comminution, loss of radial height, loss of volar tilt, radial shift, and shortening. In this regard, dorsal comminution refers to pulverization of the bone in the wrist in the direction of the back of the hand, loss of radial height refers to loss of height in the wrist on the side near the thumb, loss of volar tilt refers to loss of tilt in the wrist in the direction of the palm of the hand, and radial shift refers to shift of the wrist towards the side of the thumb. In addition, poor bone mineral quality and the degree of comminution, especially with proximal extension on the radial column, may render this fracture unstable, such that closed treatment alone may be insufficient. Further, the forces experienced by the wrist during daily activities are primarily compression, e.g., digital motion, and shear/torsion, e.g., forearm rotation. Fracture, e.g., catastrophic collapse, occurs typically in tension, thereby creating a relatively transverse fracture across the metaphysis, the metaphysis being the part of a bone between the shaft of the bone, i.e. diaphysis, and the end of the bone, i.e., epiphysis. The position of the wrist, the forces applied, and the bone quality may determine other components of the fracture, such as, for example, extension into the joint, extension into the diaphysis, and more oblique components from torsional forces.
Reduction, i.e., architectural restoration, of a simple but unstable fracture may be obtained through a variety of means. Although there has been a historical preference for non-operative treatment, more invasive treatments intended to restore cortical, i.e. external or surface, integrity have historically included pins and plaster techniques, external fixation, and cross metaphyseal pinning Later treatment techniques have included dorsal plating systems that address the radial column, and volar plate fixation. Examples of dorsal plating systems include, e.g., Forte Zimmer low profile plate or Synthes pi plate. The more rigid construct required for volar fixation, given its application on the compression side of the radius, has been purportedly outweighed by soft tissue coverage of the volar plate not afforded by dorsal plating systems.
Although plating systems may address cortical reconstitution, they do not address metaphyseal bone voids that are formed when osteopenic/osteoporotic bone collapses. Further, rigid volar plates may not adequately overcome the loss of cancellous bone in the metaphysis when significant comminution and severe loss of bony architecture has occurred. To fill these metaphyseal voids, autograft bone, banked allograft bone, and/or synthetic fillers, e.g., calcium phosphate or calcium sulfate, may be used. Moreover, although PMMA (polymethyl-methacrylate) cement has historically been used as a void filler, this material is rarely used in radius fractures since biologic and biologically active alternatives are preferred.
Plating systems and volar plate fixation may be more substantial and invasive than a patient's bone or fracture void and co-morbidities may warrant. While such fractures may frequently be reduced (architectural reconstitution) by closed manipulation and successfully casted, follow-up examination in the casting period over the next few weeks often shows that fragility fractures experience loss of reduction with resulting deformity. The typical patient with a fragility fracture is elderly and has co-morbid health conditions, which underscores the importance of minimizing risk at the same time as improving treatment methods. In these patients, it is the maintenance of the fracture reduction that is the challenge rather than obtaining a satisfactory reduction in the first place. Aggressive open fracture treatment is best avoided if it is not necessary to obtain reduction.